1. Field of the Invention
This invention relates to a sliding guide apparatus to guide, for instance, a column or a worktable for a bed of a machine tool. More particularly, it relates to a sliding guide apparatus on which an unbalanced load of a movable member acts.
2. Discussion of the Background
A conventional sliding guide apparatus guides a movable member on which sliding surfaces are formed for a base on which guide surfaces are formed with lubricating oil which is supplied between the sliding surfaces and the guide surfaces. In a case that the movable member is moved rapidly, the lubricating oil that has gotten between the sliding surface and the guide surface at the front portion of the movable member in its traveling direction generates dynamic pressure which floats the movable member. Since the front portion of the movable member is more floated than a rear portion by the dynamic pressure, the movable member is slanted. As a result, frictional force or sliding resistance of the sliding surface for the guide surface is increased, and a larger feed force is needed.
Accordingly, the inventor has invented a sliding guide apparatus which is provided with a relief means to relieve a part of the dynamic pressure to the atmospheric air so as to reduce the effect of the dynamic pressure and a sliding guide apparatus which disperses the dynamic pressure evenly along the traveling direction of the sliding surface so as to prevent the floating and the slanting of the movable member. FIG. 1 shows sliding surfaces 101 of such a sliding guide apparatus 100. Lubricating oil is supplied between the sliding surface 101 and a guide surface (not shown) that is disposed opposed to the sliding surface through supply grooves 105. A diamond-shape pocket 102 is formed on each sliding surface at the center in a traveling direction (right and left direction on the sheet) of a movable member. A relief hole 103 whose one-end is connected with the atmospheric air is opened at the center of the pocket 102 so as to relieve pressure of the lubricating oil that occurs in the pocket 102. Meanwhile, three separating grooves 104 are formed on each sliding surface 101 so as to divide the sliding surface in equal interval in the traveling direction of the movable member. A relief hole 103 whose one-end is connected with the atmospheric air is also opened in each separating groove 104 so as to relieve to pressure of the lubricating oil that occurs in the separating groove 104.
According to the sliding guide apparatus 100, the floating of the movable member that is caused by the dynamic pressure can be reduced, and the slanting of the movable member is significantly prevented. However, the floating by the dynamic pressure can not be prevented perfectly. In a case that the sliding guide apparatus is used for a machine tool in which a column or a worktable as a movable member is guided, the unbalanced load of the column or the workpiece that is set on the worktable acts on the sliding guide apparatus 100. Therefore, the column or the worktable is slanted by this unbalanced load in a state that the column or the worktable is floated by the dynamic pressure even if only a little.